In this study, a facile and effective method to modify
the photocatalytic
performance of a bismuth oxybromide (BiOBr) semiconductor through
the fabrication of a heterojunction with a hydrated bismuth oxide
(BHO) is reported. The new yBiOBr-(1 – y)BHO heterojunction, synthesized by a simple hydrothermal
method, exhibits a high photocatalytic activity under visible light
irradiation for the photodegradation of typical organic pollutants
in water, such as Rhodamine B (RhB) and acetophenone (AP). Both the
individual BiOBr and BHO components show very low photocatalytic efficiency.
Furthermore, the unique photocatalytic performance of the new hybrid
material was demonstrated through the uphill photocatalytic reaction
that involves the oxidation of potassium iodide (KI) to triiodide.
The remarkable photocatalytic activity of the coupled system is directly
related to the effectual charge carrier separation due to the formation
of the heterostructure. 0.9BiOBr-0.1BHO shows a higher photocatalytic
activity as compared with other members of the same family, 0.8BiOCl-0.2BHO
and 0.8BiOI-0.2BHO, which is directly ascribed to a synergistic effect
of the energy band-gap structure and flow of charge carriers through
the heterojunction, surface area, and light absorbance. In comparison with TiO2 (Degussa P25), the new composite material demonstrated 10.7 times
higher activity in removing aqueous RhB under visible light (λ
≥ 420 nm) irradiation. Study of the photocatalytic mechanism
proves that the degradation of RhB under visible light irradiation
over the as-prepared 0.9BiOBr-0.1BHO is mainly via a direct hole oxidation
mechanism and superoxide oxidation pathways. The resulting yBiOBr-(1 – y)BHO composites exhibit
high photocatalytic and thermal stabilities and are very promising
photocatalysts for degradation of organic pollutants in water and
for other applications.